1. Field of the Invention
The present invention relates to a suction muffler of a hermetic compressor used for a domestic electric refrigerator freezer, a display case and the like.
2. Description of the Related Art
In recent years, there has been an increasingly strong request for global environment protection, and in a refrigerator and other refrigerating cycle apparatuses, there has been a strong demand particularly for high efficiency. Conventionally, this kind of hermetic compressor is structured such that a suction muffler is directly attached to a suction hole, as shown in Japanese Translation of PCT Publication No. 2001-503833.
A description will be given below of the conventional hermetic compressor mentioned above with reference to the drawings.
FIG. 5 is a vertical cross sectional view of a conventional hermetic compressor described in Japanese Translation of PCT Publication No. 2001-503833, FIG. 6 is a cross sectional view of a substantial part of a refrigerant suction path of the hermetic compressor, and FIG. 7 is a flow rate vector diagram showing refrigerant gas behavior in the refrigerant suction path of the hermetic compressor.
In FIGS. 5 and 6, compressor main body 3 is elastically supported in hermetic vessel 1 by suspension spring 5. Further, refrigerant gas 7 is filled in hermetic vessel 1.
Compressor main body 3 is provided with electromotive element 9 and compression element 11 arranged above electromotive element 9, and electromotive element 9 has stator 13 and rotor 15.
Compression element 11 is provided with crank shaft 21, cylinder block 25, piston 27, suction valve 33, and connecting means 35. In this case, crank shaft 21 is provided with eccentric shaft 17 and main shaft 19. Cylinder block 25 forms compression chamber 23. Suction valve 33 opens and closes suction hole 31. Suction hole 31 is provided in valve plate 29 sealing an opening end of compression chamber 23. Connecting means 35 couples eccentric shaft 17 and piston 27.
Main shaft 19 is rotatably supported to bearing portion 37 of cylinder block 25. Further, rotor 15 is fixed to main shaft 19.
Further, suction muffler 41 is pinched and fixed by valve plate 29 and cylinder head 39. In this case, cylinder head 39 lids valve plate 29.
Suction muffler 41 is molded from a resin such as polybutylene terephthalate (PBT). Suction muffler 41 is provided with muffler main body 45, inlet pipe 47, and communication pipe 51. In this case, muffler main body 45 forms sound absorbing space 43. Inlet pipe 47 communicates sound absorbing space 43 and a space inside hermetic vessel 1. Communication pipe 51 has suction muffler outlet portion 49, and suction muffler outlet portion 49 directly communicates sound absorbing space 43 and suction hole 31.
Further, bent portion 53 is provided between suction muffler outlet portion 49 and communication pipe 51. Communication pipe 51 is arranged in such a manner as to extend in a vertical direction with respect to a center line passing through suction hole 31, and is fixed in such a manner that the entire region of suction hole 31 is communicated with suction muffler outlet portion 49.
FIG. 7 shows flow rate vectors 55 showing behavior of refrigerant gas 7 sucked into compression chamber 23 via communication pipe 51 obtained by a computer simulation. A length of each of the flow rate vectors 55 indicates a magnitude of the flow rate, and a direction of flow rate vectors 55 indicates a flowing direction of refrigerant gas 7. Note that, in order to easily understand the flow of refrigerant gas 7, suction valve 33 is shown by a broken line.
A description will be given below of a motion of the conventional hermetic compressor constructed as mentioned above.
First, the hermetic compressor passes a current through stator 13 to generate a magnetic field, thereby rotating rotor 15 fixed to main shaft 19. This rotates crank shaft 21 to reciprocate piston 27 in compression chamber 23 through connecting means 35 rotatably attached to eccentric shaft 17.
With the reciprocating motion of piston 27, refrigerant gas 7 is suctioned into compression chamber 23, compressed, and then discharged to a refrigerating cycle (not shown) in repeating fashion.
Refrigerant gas 7 returned from the refrigerating cycle in a suction stroke is introduced into compression chamber 23 via suction hole 31 communicating with compression chamber 23 according to the opening and closing of suction valve 33, through suction muffler 41.
In this case, suction muffler 41 reduces a noise generated by an intermittent suction of refrigerant gas 7. Further, since suction muffler 41 is formed by a resin having a low thermal conductivity, it prevents refrigerant gas 7 passing through the inside of suction muffler 41 from being heated.
Further, suction muffler outlet portion 49 is communicated directly with suction hole 31, thereby preventing the noise from leaking. Further, suction muffler outlet portion 49 is communicated directly with suction hole 31, thereby preventing refrigerant gas 7 having a high temperature and heated by electromotive element 9 or the like from being sucked in hermetic vessel 1.
However, in the conventional structure mentioned above, since communication pipe 51 and suction muffler outlet portion 49 have bent portion 53 which is vertically bent, dead water region (area) 57 having no flow of refrigerant gas 7 is generated in an inner peripheral side of bent portion 53, as shown in FIG. 7. Since dead water region 57 is formed, a flow path area of refrigerant gas 7 becomes small. Accordingly, in suction muffler outlet portion 49, a density (a flow rate) of refrigerant gas 7 flowing through communication pipe 51 becomes more in an outer side of bent portion 53 than that in dead water region 57 side, refrigerant gas 7 is concentrated on a downstream side, and more refrigerant gas 7 flows while increasing a flow rate. Therefore, dead water region 59 having no flow of refrigerant gas 7 is generated in suction hole 31, an effective area coming to the refrigerant gas passage of suction hole 31 becomes small, and there is a problem of deteriorating volumetric efficiency.